Electrolytic recording paper containing a polyhydroxy benzene marking compound and an organic dicarboxylic acid



United States Patent Ofifice 3,354,058 Patented Nov. 21, 1967 3,354,058 ELECTROLYTIC RECORDING PAPER CONTAIN- INC A POLYHYDROXY BENZENE MARKING COMPOUND AND AN ORGANIC DICARBOX- YLIC ACID Robert S. Ives, Lexington, Mass., assignor to Milton Alden, Needharn, Mass. No Drawing. Filed Oct. 7, 1963, Ser. No. 314,534 14 Claims. (Cl. 204-2) ABSTRACT OF THE DISCLOSURE An electrolytic recording material comprising a support impregnated with a water solution containing a strong electrolyte, a lake forming polyhydroxy benzene, and an organic dicarboxylic acid selected from the group consisting of phthalic acid, hydrogenated phthalic acid and nadic acid or the anhydrides thereof.

This invention relates to electrolytic recording paper of the electrochemical type employed in facsimile recorders.

In one well-known system of such recording the paper is impregnated with a water solution of a strong electrolyte and a polyhydroxy benzene which combines with the metal of the electrode under the influence of a modulated electric current to form a colored lake, thereby forming the record. It is also known that the addition of oxalic and maleic acids to the impregnating solution is advantageous to increase the stability of the paper prior to recording and to increase the sharpness and detail of the final record. Thiourea and phosphates can also be employed as stabilizers.

The above recording paper does not form a record with as much contrast between the record and the background as is desirable for good legibility. It is accordingly the main object of this invention to provide an improved recording paper utilizing a lake-forming polyhydroxy benzene which gives a darker record with improved legibility.

According to this invention, this object is achieved by providing an electrolytic recording material for recording with a lake-forming metal electrode comprising a support impregnated with a water solution containing a strong electrolyte, a lake-forming polyhyd-roxy benzene and an organic dicarboxylic acid, or anhydride thereof, selected from the group consisting of phthalic acid, hydrogenated phthalic acid, and nadic acid. Where only the above acids or anhydrides are used, the amount is preferably between about 2% and 4% by weight of solutes in said solution. If these acids are combined with other acids such as oxalic acid, the combined weight of all acids and anhydrides are preferably within these limits.

The above acids serve to stabilize the impregnated paper and in addition form a darker mark with the polyhydroxy phenol under the influence of the recording current. This darker mark which improves the legibility of the final record is believed to be due to the fact that the acids also form a colored precipitate with the electrode metal at the point of recording.

Suitable lake-forming polyhydroxy benzenes include catechol, sodium catechol monosulfonate, dihydroxyphenyl-acetic acid, resorcinol and a sodium naphthol disulfonate, catechol being the preferred material. Suitable lake-forming electrode metals are iron, chromium, copper and nickel, while suitable electrolytes include the chlorides, bromides and nitrates of caesium, rubidium, potassium, sodium or lithium.

This invention is illustrated by the following examples, acid anhydrides being employed since these are commercially available materials:

Example 1 Gm.

Catechol 5 Potassium nitrate 10 Phthalic anhydride 0.5 Water to cc.

Example 2 Catechol 5 Potassium nitrate 10 Tetrahydro phthalic anhydride 0.5 Water to 100 cc.

Example 3 Resorcinol 5 Potassium nitrate 10 Hexahydro phthalic anhydride 0.5 Water to 100 cc.

Example 4 Catechol 5 Potassium nitrate 10 Nadic anhydride 0.5

Water to 100 cc.

Nadic anhydride is the name given by National Aniline Division, Allied Chemical and Dye Corp., for endo-cis bicyclo [2.2.1]-5-heptene-2,3-dicarboxylic anhydride of the following structure H /C\ ii H0 CH-C\ n I HO CH--O \O/ g Example 5 Catechol gm 5 Potassium nitrate gm 17 Phthalic anhydride gm 0.5 Thiourea gm 0.22 NaH PO -H O gm 0.22 Water cc Example 6 Catechol m 5 Potassium nitrate gm l7 Phthalic anhydride gm 0.5 Thiourea gm 0.22 NaH2PO4H2O gm Oxalic acid cm 0.1 Water cc 160 Example 7 Dihydroxy phenyl acetic acid gm 9 Potassium nitrate 2m 18 Phthalic anhydride gm 0.5 Water cc 100 As more fully disclosed in my copending application, Ser. No. 286,951, filed June 11, 1963, a sequestering or chelating agent can be added to the foregoing examples to improve definition by controlling trailing of the record after recording ceases. For example, 0.6 gm. of Seqnestrene Na2 can be added to Example 1 or 0.3 gm. to Example 7. Seqnestrene Na2 is the trademark of the Alrose Chemical Co. for a solution of amino carboxylic acids. The various anhydrides shown in the foregoing examples hydrolize in the presence of Water to form a corresponding dicarboxylic acid. To facilitate this hydration, mild heat may be employed but is not necessary since hydrolysis occurs at room temperatures although more slowly.

A support such as paper canbe impregnated with any of the above solutions by passing it through a 'bath of the solution. Suitable conditions are immersion at room temperature to provide, preferably about 30 to 50% by weight moisture in the, support.

Itrshould be understood that this disclosure is for the purpose of illustration only and that the invention includes all equivalents and modifications falling within thescope of the appended claims.

I claim:

1. An electrolytic recording material for recording with a lake-forming metal electrode, comprising a support impregnated with a water solution containing a strong electrolyte, a 'lak'erorming 'polyhydroxy benzene, and an organic dicarboxylic acid selected from the group consisting of phthalic acid, hydrogenated phthalic acid, nadic acid and anhydrides thereof.

2. Electrolytic recording .material according to claim 1 whereinsaid acid is present in .an amount'from about 2 to 4% by weight ofsolutes :in said solution.

3. Electrolytic recording material according-to claim 1 wherein said polyhydroxy benzene is catechol and said acid is phthalic anhydride.

4. "Electrolytic recording material according to claim 1 wherein said polyhydroxy benzene is catechol and said acid i's'te'trahydro phthalic arihydride. v I

5. Electrolytic recording material according to claim 1 wherein said polyhydrox'y benzene "is catechol and said acid is .hexahydro :phthalic anhydride.

.6. Electrolytic recording material according to claim 1 wherein said polyhydroxy benzene "is catechol and said acid is nadic anhydride.

7. Electrolytic recording material according to claim 1 wherein said polyhydroxy benzene is dihydroxy-phenylacetic acid.

8. An electrolytic recording material for recording with a lake-forming metal electrode, 'com'prising a paper support impregnated withfan aqueous solution containing an electrolyte in an amount suificient to render said paper conductive, a lake-forming polylhydroxy benzene marking compound in an amount sufficient to form a visible record in response to current passing through said paper, said marking compound being selected from the group" consisting of catechol, sodium catechol monosulfonate, resorcinal, dihydroXy-phenyl-acetic acid, and sodium naphthol disulfonate, and an organic acid selected from the group consisting of phthalic acid, hydrogenated phthalic acid, nadic acid, and anhydrides thereof, said organic acid being present in an amount between about 2 to 4% by weight of the solutes in said solution.

9. Electrolytic recording material according to claim 1 further containing means for controllingtrailing of record comprising a sequestering agent for said electrode metal in an amount suflicien't'to retard record formation in nonrecord areas of said support.

10. Electrolytic recording material according to claim 9 wherein said means comprises from about 0.3 to 0.6 gram per 160 cc. impregnating solution.

11. Electrolytic recording material according to claim 9 wherein said polyhydroxy benzene is dihydroxy-phenylacetic acid.

12. Electrolytic recording material according to claim 11 wherein said support is paper and said means comprises from about 0.2 to 0.6 gram of an amino-carboxylic acid per 160cc. impregnating solution.

13. The method of electrolytic recording which comprises .passing a record support between recording electrodes, said record being impregnated with an aqueous solution according to claim 1.

1-4. The method of electrolytic recording which comprises passing a paper support between recording electrodes, said support being impregnated with an aqueous solution according to claim 8.

References Cited UNITED STATES PATENTS 3,074,809 1/1963 Owen 1-17- 368 3,216,855 I I/51965 Ellison a 11'7--2 16 JOHN MACK, Primary Examiner.

W. VAN-SISE, Assistant Examiner. 

1. AN ELECTROLYTIC RECORDING MATERIAL FOR RECORDING WITH A LAKE-FORMING METAL ELECTRODE, COMPRISING A SUPPORT IMPREGNATED WITH A WATER SOLUTION CONTAINING A STRONG ELECTROLYTE, A LAKE-FORMING POLYHYDROXY BENZENE, AND AN ORGANIC DICARBOXYLIC ACID SELECTED FROM THE GROUP CONSISTING OF PHTHALIC ACID, HYDROGENATED PHTHALIC ACID, "NADIC" ACID AND ANHYDRIDES THEREOF. 